"Pen tool is a part of Illustrator.Illustrator is a part of Grapics Design.pen tool is the most important tool in Illustrator.Now, I am going to telling you how to use this tool. *Actually we use the pen tool to create drawing paths. You can create custom shape and complicated curves that can be scaled easily.by accessing the expanded Pen tool,you can add delete and covert points on your drawing path.it has 8 types.As 1.Ready to draw a path.2 Position over a path to add a point.3 position point over to remove a point. 4.Position point over end of an open path to countinue drawing that payh with the pan tool.5. Close a path.6. Countinue drawing a path 7.Position the pointrt over a point and the convert point icon appears. 8.When the ALT(Windows) or option (Mac OS) Key is held down , it converts to the convert Anchor point tool. *Its allow you to define your own anchor points, as well as adjust the curve associated with those anchors, simply by manipulating two control points associated with each anchor. In other words, to create a line, you first define two anchor points."